[Android] You can specify where different book formats are to go on your device, e.g., epubs in one folder, pdfs in another, and mobis in a third.

Calibre Companion updates the metadata for the books on every connect as a wireless device, ensuring the information for your books displayed in Calibre Companion is the same as the information displayed in calibre.

Most setup is on the device, making it easy for different users in the same household to have different device configurations, or to use more than one computer running calibre.

The third: Calibre Companion can access your library via calibre’s content server or the cloud.
Using just your device, you can:

You must also already use calibre to manage your library of ebooks. CC gets books only from calibre.

By default, CC imports the book file (and its metadata) into your device. If you don’t have much storage on your device, it is recommended that you use CC as a catalogue/database instead or only import the few that you are going to read soon. This is particularly recommended for users with comics, which tend to have very large book files.